With recent elucidation of physiological roles of calcium, various calcium antagonists having various chemical structures have been studied and have been come into the market. There have now been used the calcium antagonists such as nifedipine, diltiazem hydrochloride, etc. for the prophylaxis and treatment of various diseases such as ischemic heart disease, hypertension and the like. These medicaments have, however, comparatively short duration of action, and hence, it has been desired to find a medicament having more prolonged activity.
As far as the present inventors know, there is no report that a tricyclic or tetracyclic compound having .omega.-[4-substituted-1-(homo)piperazinyl]alkanoylamino group has a calcium antagonistic activity.
The present inventors have intensively studied in order to obtain novel compounds having a chemical structure different from the known calcium antagonists and having superior activity to the latter, and have found that tricyclic or tetracyclic compounds having .omega.-[4-substituted-1-(homo)piperazinyl]alkanoylamino group show potent calcium antagonistic activity when they satisfy the following conditions:
(i) the substituent at 4-position of the (homo)piperazinyl group contains at least one aromatic hydrocarbon group or aromatic heterocyclic group, and
(ii) the middle ring of the tricyclic or tetracyclic group is a seven-membered ring, and further that some of them show more prolonged antihypertensive activity than that of the commercially available calcium antagonists.